As has been known for many years, a unique way of producing nickel of high purity entails the formation and subsequent decomposition of nickel tetracarbonyl. While nickel refining by means of such a procedure has been practiced on a commercial scale, great care and elaborate safety measures are dictated by the well known toxicity of nickel carbonyl. Concern over the toxicity has led to regulations setting extremely low levels for the amount of nickel carbonyl which may be present in the atmosphere of an industrial plant. In one case a threshold value of 1 part per billion (ppb) by volume was as the maximum concentration of nickel carbonyl which may be present. Compliance with such stringent regulations has created a need for extremely sensitive detection equipment, capable of measuring such trace amounts in air samples taken from a workplace.
Various methods have been developed in the past for measuring small amounts of carbonyl gas. These include methods relying on chemical collection and analysis, plasma chromatography and infrared spectroscopy. None of these techniques has been able, however, to satisfy the needs for a piece of equipment which possesses not only sensitivity to minute levels and an acceptably fast response but also compactness to ensure its portability between locations in an industrial plant.